To access a wireless local area network (WLAN) a user equipment (UE) first needs to search for a WLAN. Searching for a WLAN includes active scanning and passive scanning. In the active scanning, the UE actively sends a probe request, and then if a WLAN access point (AP) returns a probe feedback (for example, a probe response), it indicates that the search is successful. In the passive scanning, a WLAN AP sends a beacon once at each beacon interval, and if the UE successfully receives the beacon, it indicates that the search is successful. After a WLAN AP is successfully found by means of active scanning or passive scanning, the UE may initiate a connection request (for example, an association request) to the found WLAN AP for connection.
In active scanning, it is assumed that a UE searches for a WLAN every 15 s, and there are 11 WLAN channels in total. The UE stays on each WLAN channel for approximately 5 ms, where 1 ms is used to send a probe request, and power consumption is approximately 250 mA*s and the remaining time is used to search for a probe feedback, and power consumption is approximately 60 mA. Power consumption consumed in other sleep time is approximately 180 μA*s. Therefore, it may be learned by calculation that total energy consumed by the UE within 15 s is 8.08 mA*s. In passive scanning, a UE is always in a process of searching for a probe feedback, and if a cycle of broadcasting a beacon by a WLAN AP is 1 s, in the worst situation, energy consumed within 1 s is 60 mA*s. Relatively speaking, power consumption for active scanning is less than that for passive scanning. However, in cases of some frequencys or in some scenarios, active scanning is prohibited. Therefore, how to reduce power consumption for passive scanning is a problem that needs to be resolved.